Over the past several years we have developed a viable in vitro preparation of the mammalian retina in which it has been possible to record intracellulary the responses to photic stimulation of retinal neurons and to correlate neuronal response properties with neuronal morphology by means of intracellular staining techniques. Eyes, enucleated from anesthetized anticoagulated cats, are arterially perfused with an artificial medium composed of 60% Eagles tissue culture medium and 40% newborn calf serum saturated with 95% 02, 5% CO2. The anterior portions of the eye are removed allowing direct access to the retina, which remains viable for 6 to 9 hours. We are presently accumulating electrophysiological and morphological information on cat retinal neurons and find that the cat retina is a complex piece of central nervous tissue containing some 20 to 25 different neuronal types.